Patent GB-420435-A (GB)
Title: Improvements in electric motor control systems
IPC: H02P5/68
Filed: 1933-05-24
Abstract: 420,435. Equalizing load on generators. STUBBS, A., 390, Wilbraham Road, Chorlton-cum-Hardy, Manchester, PERRY, J. F., The Cottage, Bolham, Tiverton, Devon, STUCKEN, S., 19, Moreton Avenue, Stretford, Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. May 24, 1933, No. 15038. [Class 38 (iv)] An electric motor WM, e.g. a winder motor, is supplied from A.C. mains through a grid controlled arc rectifier V1 in parallel with a D.C. generator G which is provided with a flywheel FW and the excitation of which is varied with the grid excitation of the rectifier V1 so that the load peaks of the motor are supplied by the flywheel and the output of power from the mains is restricted in a predetermined manner. The excitation of the generator G is controlled by a hand-lever L operating on a resistance GR and having three forward and three reverse positions. The lever L also operates through non-reversible linkage U and a lost motion connection 22 on the rotor of an induction regulator IR1 which controls the grid excitation of the rectifier V1 and which has a movable stator operated by a torque motor T1 in response to mains current so as to limit the rectifier output. In its first position the lever L causes energization of a solenoid PS acting on the regulator IR1 so that the output of the rectifier V1 to the fly-wheel motor G is maximum and this motor is speeded up. In the second position of the lever L the coil PS is de-energized and the regulator IR1 is moved by the spring S2 so that the rectifier V1 delivers minimum voltage. In the third position the forward or reverse contactor coil OCF or OCR operating on contacts in the circuit of the motor WM or its excitation circuit, closes the connection between the motor and the generator G which is now lightly excited and the rectifier V1 is controlled to give a low voltage. The motor WM is speeded up, the peak load being taken from the generator G and control being effected by the lever L being moved in its third position over the resistance GR and at the same time controlling the regulator IR1. In the event of excess load the torque motor T1 moves to reduce the output of the rectifier V1 and the peak load is supplied by the generator G. Reverse operation occurs when the lever L is moved back. The excitations of the motor WM and generator G may be supplied from exciters driven by an A.C. motor coupled to the mains or from a separate grid controlled rectifier V3. In a modification the generator G is driven by a motor supplied from the mains through an additional rectifier grid controlled by an induction regulator having one fixed winding the other being rotatable by a torque motor in response either to current in the mains or to the operation of a contactor which is open in the first position of the lever L so as to allow current control only to operate on the rectifier so that it delivers its maximum voltage to the motor to speed up the generator G, a contactor controlling the torque motor T1 operating on the main rectifier V1 being in this position closed so that the regulator IR1 is moved to the position in which the rectifier V1 is delivering no current. In the second positions the rectifier conditions are the same but one of the motor contactors is closed and the motor WM is started. At the same time the generator excitation is being gradually increased. In the third position of the lever L the induction regulator of the auxiliary rectifier is operated in response to energization of its contactor control so that the rectifier supplies no current to the motor driving the generator G, the contactor controlling the torque motor T1 is de-energized and the rectifier V1 supplies current to the motor WM, the speed of which is now subject to the position of the lever L which determines the generator excitation and the control of the rectifier V1. When the regenerative effect of the motor WM is used a relay dependent on the speed of the flywheel shaft is arranged to operate the torque motor controlling the auxiliary rectifier so as to limit the speed of the motor driving this shaft. This motor may alternatively be an A.C. motor controlled by a slip regulator or by a suitable form of hydraulic coupling. In a modification instead of the generator field being controlled by resistance GR operated from the lever L, the generator field may be controlled by a vibrating type regulator so as to match the generator voltage to that supplied by the rectifier V1 in a predetermined manner. In a further modification the action of the lever L may be subject to an over-riding control by a cam driven from the drum D of the winding motor so as to be responsive to depth. Alternatively the whole control may be made responsive to depth by controlling the arm of the lever L from a depth-responsive cam, the apparatus being then automatic, and forward and reverse starting and stopping being effected by push buttons controlling the forward and reverse motor contactor coils which are also provided with holding contacts. The stopping may also be controlled by a switch in the motor contactor circuit responsive to over-winding.